Aromatic chalcogenazolium salts, such as benzoxazolium, naphthoxazolium, benzothiazolium, naphthothiazolium, benzoselenazolium, and naphthoselenazolium salts, as well as their azole, azoline, and azolinium derivatives, have been widely employed in silver halide photography. These compounds have been employed as nuclei in antifoggants or stabilizers, nucleating agents, latent image keeping addenda, and speed or contrast increasing addenda for silver halide photographic systems.
Aromatic chalcogenazolium salts are commonly incorporated as nuclei of polymethine dyes. A well known method for the synthesis of carbocyanine dyes employs 2-(2-acetanilidovinyl) substituted aromatic chalcogenazolium salts as intermediates, the latter being formed by reacting an N,N'-diarylformamidine with an aromatic chalcogenazolium salt substituted at its 2 ring position with a methine precursor, such as a methyl group, followed by treatment with a base and acetylation, either sequentially or concurrently. Carbocyanine dye synthesis can be completed by reacting the 2-(2-acetanilidovinyl) substituted aromatic chalcogenazolium salt with another azine or azole heterocycle also ring substituted with a methine group precursor, such as a 2-methyl substituted azole or 2- or 4-methyl substituted azine. Such carbocyanine dyes syntheses are illustrated by T. H. James, The Theory of the Photographic Process, 4th Ed., Macmillan, 1977, pp. 205-212, and by F. M. Hamer, Cyanine Dyes and Related Compounds, John Wiley and Sons, 1964, pp. 105, 106, and 117-120.
Although Schlichting U.S. Pat. No. 2,168,174 and Wilson U.S. Pat. Nos. 2,323,503 and 504 have extended generic ring formulae to include tellurazoles as extrapolations of investigations of other chalcogenazoles, the true state of the art is summed up by Middleton, U.S. Pat. No. 2,339,094:
"It may be observed that the difficulty of reaction resulting in the production of azoles containing members of the oxygen group of elements in the azole ring may vary greatly with different elements, becoming greater in proceeding from the non-metallic elements such as oxygen and sulfur to the more strongly metallic elements such as selenium and tellurium. This probably accounts for the fact that many of the oxazoles and thiazoles have been known for years while the preparation of most of the selenazoles has been accomplished more recently and some of them are still unknown although the corresponding oxazoles and thiazoles are known. Furthermore, the tellurazoles from the simplest to the more complex derivatives have not been described up to the present time."
While the art has heretofore been unsuccessful in preparing tellurazolium salts and their derivatives, it should be noted that divalent tellurium atoms have been placed in other ring structures. Benzisotellurazole-1,2 is described in "Un Nouvel Heterocycle Tellure: 1e Benzisotellurazole-1,2", by Campsteyn et al, Journal of Heterocyclic Chemistry, Vol. 15, August 1978, pp. 745-748. Unfortunately no derivative of benzisotellurazole-1,2 is disclosed.
Tellurium atoms have been incorporated in ring structures other than azole or azine rings of various dyes. Japanese Kokai No. 136420, laid open Nov. 25, 1976, discloses a 1-tellura-3,5-cyclohexanedione nucleus in a merocyanine sensitizing dye in a silver halide emulsion. Detty et al U.S. Pat. No. 4,329,284 discloses 1,2-oxachalcogenol-1-ium salts, wherein the chalcogen can be tellurium or selenium, to be useful in photoconductive compositions. Detty et al U.S. Pat. Nos. 4,365,016 and 4,365,017 disclose tellurapyrylium dyes for use in photoconductive compositions.
In Gunther et al. U.S. Pat. No. 4,576,906 there are disclosed compounds containing an aromatic ring portion fused with a tellurazolium or derivative tellurazole, tellurazoline (including tellurazolinylidene), or tellurazolium ring portion together with processes and intermediates for their preparation.